title: Epigenetic regulation of organic anion transporting polypeptide 1B3 in cancer cell lines.
abstract: OBJECTIVE
  The expression of a multispecific organic anion transporter, OATP1B3/SLCO1B3, is associated with clinical prognosis and survival of cancer cells. The aims of present study were to investigate the involvement of epigenetic regulation in mRNA expression of a cancer-type variant of OATP1B3 (Ct-OATP1B3) in cancer cell lines.
  
  
  METHODS
  The membrane localization and transport functions of Ct-OATP1B3 were investigated in HEK293 cells transiently expressing Ct-OATP1B3. DNA methylation profiles around the transcriptional start site of Ct-OATP1B3 in cancer cell lines were determined. The effects of a DNA methyltransferase inhibitor and siRNA knockdown of methyl-DNA binding proteins (MBDs) on the expression of Ct-OATP1B3 mRNA were investigated.
  
  
  RESULTS
  5'-RACE identified the TSS of Ct-OATP1B3 in PK-8 cells. Ct-OATP1B3 was localized on the plasma membrane, and showed the transport activities of E217βG, fluvastatin, rifampicin, and Gd-EOB-DTPA. The CpG dinucleotides were hypomethylated in Ct-OATP1B3-positive cell lines (DLD-1, TFK-1, PK-8, and PK-45P) but were hypermethylated in Ct-OATP1B3-negative cell lines (HepG2 and Caco-2). Treatment with a DNA methyltransferase inhibitor and siRNA knockdown of MBD2 significantly increased the expression of Ct-OATP1B3 mRNA in HepG2 and Caco-2.
  
  
  CONCLUSIONS
  Ct-OATP1B3 is capable of transporting its substrates into cancer cells. Its mRNA expression is regulated by DNA methylation-dependent gene silencing involving MBD2.
authors.affiliation: Laboratory of Molecular Pharmacokinetics Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, Japan.
authors.forename: Satoki
authors.initials: S
authors.lastname: Imai
authors.forename: Ryota
authors.initials: R
authors.lastname: Kikuchi
authors.forename: Yuri
authors.initials: Y
authors.lastname: Tsuruya
authors.forename: Sotaro
authors.initials: S
authors.lastname: Naoi
authors.forename: Sho
authors.initials: S
authors.lastname: Nishida
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kusuhara
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Sugiyama
mesh_terms: D002460:Cell Line; D045744:Cell Line, Tumor; D019175:DNA Methylation; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D044127:Epigenesis, Genetic; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D009369:Neoplasms / Q000235:genetics* / Q000378:metabolism; D029362:Organic Anion Transporters, Sodium-Independent / Q000235:genetics* / Q000378:metabolism; D034622:RNA Interference; D012333:RNA, Messenger / Q000235:genetics; D000074542:Solute Carrier Organic Anion Transporter Family Member 1B3
chemical_list: D004268:DNA-Binding Proteins; C115368:MBD2 protein; D029362:Organic Anion Transporters, Sodium-Independent; D012333:RNA, Messenger; C421209:SLCO1B3 protein, human; D000074542:Solute Carrier Organic Anion Transporter Family Member 1B3